On dense water formation criteria and their application to the Mediterranean Sea

Recently proposed criteria to identify sites, periods and characteristics of dense water formation in the Mediterranean Sea are analyzed. These criteria were first obtained through tank experiments and numerical and theoretical analyses. They can be useful for discriminating between processes that reach the sea bottom and those involving only the less thick superficial layers. With these criteria, general characteristics of newly formed dense water can be inferred from a knowledge only of winter density stratification g', of the buoyancy increase B due to the violent winter storms, and of the horizontal space scale R of the region of interest, a quantity usually identified by a decrease of 0.5-1 degrees C of the SST. For the Mediterranean Sea, these criteria are applied here to the few known field observations and to more indirect "routine" information, namely climatological values of the stratification, numerical estimates of the buoyancy flux and remotely sensed SST from satellite imagery. In this way a. stimulating picture of these dramatic phenomena is obtained, giving some insight into the possibility of forecasting and into other characteristics of dense water formation processes. (C) 1999 Elsevier Science Ltd. All rights reserved.